Moments, couples and centre of massAQA A-Level Physics: Mind map

Exam questions on Moments, couples and centre of mass

1. A mechanic tightens a nut with a spanner. The force is applied at the end of the handle, at a distance of 0.35 m from the centre of the nut. The force has a magnitude of 120 N.
   To loosen a stubborn nut a longer spanner is used, so that the same moment of 42 N m is produced by a force applied at right angles at a distance of 0.60 m from the nut. Calculate this force.2 marks
2. A driver turns a steering wheel of diameter 0.36 m by pulling down with one hand with a force of 8.0 N on one side of the rim and pushing up with the other hand with a force of 8.0 N on the opposite side. Both forces are tangential to the rim.
   Explain why the wheel turns but is not pushed sideways by the driver's hands.2 marks
3. A uniform beam of length 4.0 m and weight 120 N is supported by a pivot. A child of weight 300 N sits on the beam at a point 0.50 m from its left end. The beam is horizontal.
   The pivot is under the centre of the beam. A second child of weight 450 N sits on the other side of the pivot and the beam balances horizontally. Calculate the distance of the second child from the pivot.3 marks